Mikami T, Genma R, Nishiyama K, Ando S, Kitahara A, Natsume H, Yoshimi T, Horiuchi R, Nakamura H
Department of Internal Medicine, Hamamatsu University School of Medicine, Shizuoka, Japan.
Metabolism. 1998 Sep;47(9):1083-8. doi: 10.1016/s0026-0495(98)90282-7.
Protein disulfide isomerase (PDI) is an enzyme that participates in the formation of disulfide bonds. It is also known to be the subunits of some enzymes and the membrane-associated thyroid hormone-binding protein. In this study, we measured the quantitative distribution of PDI protein in rat tissues and examined the relationship between protein level and enzyme activity in PDI during fasting and refeeding. Western blotting with specific anti-PDI antiserum detected the PDI protein band of 55 kd. Among several tissues, liver contained the largest amount of PDI protein, followed by kidney and fat, in which one-third to one-fourth of the hepatic PDI protein existed. The PDI protein band was also detected in heart and muscle. Fasting for 3 days decreased PDI protein levels in rat liver by 40%; control levels were recovered after 3 days of refeeding. The same change was observed in kidney. PDI activity, measured by the scrambled ribonuclease method, did not show the parallel alteration to PDI protein level in liver and kidney. Isomerase activity decreased to 50% of control values during fasting, but did not recover by refeeding. Thyroidal status did not affect either PDI protein level or isomerase activity. These findings show that fasting and refeeding affect PDI protein and enzyme activity, and that PDI protein level does not always reflect PDI activity.
蛋白质二硫键异构酶（PDI）是一种参与二硫键形成的酶。它也被认为是某些酶的亚基以及膜相关甲状腺激素结合蛋白。在本研究中，我们测定了大鼠组织中PDI蛋白的定量分布，并研究了禁食和再喂养期间PDI蛋白水平与酶活性之间的关系。用特异性抗PDI抗血清进行的蛋白质印迹法检测到55kd的PDI蛋白条带。在几种组织中，肝脏中PDI蛋白含量最高，其次是肾脏和脂肪，其中脂肪中的PDI蛋白含量为肝脏的三分之一到四分之一。在心脏和肌肉中也检测到了PDI蛋白条带。禁食3天使大鼠肝脏中的PDI蛋白水平降低了40%；再喂养3天后恢复到对照水平。在肾脏中也观察到了相同的变化。用核糖核酸酶错配法测定的PDI活性在肝脏和肾脏中并未与PDI蛋白水平呈现平行变化。禁食期间异构酶活性降至对照值的50%，但再喂养后并未恢复。甲状腺状态对PDI蛋白水平或异构酶活性均无影响。这些发现表明，禁食和再喂养会影响PDI蛋白和酶活性，并且PDI蛋白水平并不总是反映PDI活性。
